CAV Filters - Education please

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Gypsy

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Can somebody tell me what CAV means. I read that they are well respected filters for diesel but what other types are there?

And to further my education...I have a Volvo D2-55 (Perkins) which was installed with a pre-filter plus bowl. The bowl was metal (as I believe is required for commercial marine installations) so it did not help me see water or gunk collected. I recently replaced it with a Racor 250 filter assembly which has a transparent bowl - I feel much better being able to see my dirty gunk collecting - but now I am starting to exercise my mind about filter specifications.

The Racor filter insert is a 30 micron grade and that seems to be considered adequate as a pre-filter, but I am interested to know what the "grade" or spec is of the Volvo filters, the pre-filter #3581078 and the final engine mounted filter #861477. Does anybody have specs on these or can point me to a source?
Thks
 
This information is surpisingly hard to find, but 5 microns is typical for the engine filter.(ie CAV/DELPHI 296 and equivalents).
 
I have a CAV filter as a pre-filter on my Yanmar 1GM.

I have for some time been casting suspicious looks at it as the culprit of my ongoing air-in-the-diesel saga. Because it is made up of four parts - cartridge, glass bowl, top and bottom castings plus the bolt and seals top and bottom - you end up with five seals to leak /forums/images/graemlins/confused.gif.

The only real advantage is that the cartridges are very cheap - the worry may initiate a change to a Racor however - views sought!!!

I think the theory is that the pre-filter should be 20 or 30 micron to get rid of the real gunk and aglomerate the water and you should then have a finer 10 micron filter on the engine - which I do.

After excavating about 15 litres of s**t from the bottom of my tank several weeks ago I fully realise the importance of good frequently changed filters.
 
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The only real advantage is that the cartridges are very cheap - the worry may initiate a change to a Racor however - views sought!!!



[/ QUOTE ]

I suffered with a CAV filter for years until fitting a Racor unit last year. Worth every penny. I've just changed filters for the first time and it was a pleasure, compared to the drag of previous years.
 
If you have a CAV filter with a plastic drain plug at the bottom that can also leak air. We had a problem with ours when we first got RedBoat, and we only found the leak by chance when we hung an inspection lamp behind the filter to look for something else. Somewhat strangely, it didn't leak diesel the other way.
 
Take the CAV filter out of its box and study it carefully + then throw it away.

Get a raccor one with a water trap in the bottom of it.
 
I personally have no reason to complain about my CAV filter /forums/images/graemlins/blush.gif

I just replace the orings coming with the cartridge and it works faultlessly.

I thought about changing to Racor but here Racor cartridges come at around 30euro, whereas CAV cartridges are 3/4 euro only /forums/images/graemlins/ooo.gif
 
Take the CAV filter out of its box and study it carefully + then throw it away.


/forums/images/graemlins/laugh.gif

Now don't be like that! They aren't that bad!

However, as we have said before, the Racor housings and filters are easier to change and very efficient. The only problem is they only do them as 30 micron and 2 micron. The CAV standard is a nominally rated 5 micron. However, IMHO the majority of rubbish you want a pre-filter to stop is above 30 micron anyway + water which the Racor is much more efficient at seperating out so there is no problem going from 5 to 30 and the capacity to hold dirt before becoming blocked will be phenominally improved. Anything that does get through will be stopped by your "last chance" filter which is 2 micron anyway. If you are in the habit of changing this once a season then a Racor 30 micron upstream will do a better job for you than the CAV one will.
 
I would agree actually. Personally the only problem I really have with the CAV ones is that everything they stop sits on the upside of the filter and they are rubbish as a water seperator because they were actually never designed as a water seperator in the first place! They are much messier to change than a Racor though, but if you can live with that they are fine. People habitually do the centre bolt up far to tight and distort the housing and then complain because they leak. Use a smaller spanner!
 
you should then have a finer 10 micron filter on the engine - which I do.
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I hope not! The last chance filter on the engine is usually 2 micron. Anything courser than that is putting your fuel pump at risk.
 
I can out pedant that........ the A is for Anthony! ( I served my time with CAV/Rotax before Lucas bought them out) /forums/images/graemlins/smile.gif
 
The comment by boatmike is coerrect about the CAV ability to deal with water however the HD suffix on the Delphi filter refers to heavy duty where apparently a more robust cartridge media is used that is more effective at stripping water from the fuel.

At the end of the day the cav system offers a cheap but effective filtration that is surapased by the simplerb and more effective racor filters. However with a well managed fuel system we should not have to change filters more often than every 6 months to a year so for a cash strapped pauper like me cav works! I did enquire about the change over adapter but found that it would be just as cheap (or expensive) to renew the filter housing complete. I also think the Racor only goes down to 30 micron where the cav betters this thus protecting my expensive volvo spin on on the engine with the cheap "chucker" on the cav.

I know i'll eat my words one stormy night upside down in the cockpit locker with a torch in my gob and a broken glass in my hand..... but i hope to maintain myself out of this situation and will continue to persevere with the cav system.
 
Must agree with BoatMike in all respects. I have been CAVing since I first came across them in the early 1970s.
I must be doing something wrong, but in my exprience once you have mastered the technique of changing they are good simple cheap filter that protects the fuel system very well.

I have kept looking once a year to see if any bugs have signed up to sail with me but by keeping the tank topped up as far as possible and regular draining off of any condensate the bugs seem to prefer to berth in other's tanks to mine thus I only seem to get through one filter a year for 16 years now on my yacht.

Brian
 
Thanks Vince for the specific answer to CAV and to all the other poster's comments to assist my education. It seems I have been lucky? not to have dealt with "messy" CAV filters.

As to the specs for the Volvo filters, they may stay part of the "secret mens business of diesel engines" but it seems likely that the one engine mounted unit is 2 or 3 micron.
 
This is precisely our experience too over many years. There is a knack I guess, but I don't know what it is! All I do know, is that we NEVER have a single drop of diesel appear from the unit once it's tightened up. /forums/images/graemlins/smile.gif

Oh, maybe that's it, we do not over-tighten the thing. By coincidence a pal and me had a chat in the yard about this problem on Sunday. He actually removes the whole unit to assemble the parts, then re-installs it!! He showed it to me and I tried to turn the bolt to release the sections - wow! it was done up incredibly tight and one of the seals had been displaced a bit - result, leak! /forums/images/graemlins/frown.gif /forums/images/graemlins/confused.gif
 
After a traumatic few minutes due to the engine deciding it didn't want to play after a rather bumpy trip with the fuel tank low, I decided that I'd never be able to change a CAV filter at sea, at least, not when it's bumpy, the engine's just hot enough to hurt and I need the engine NOW.

Since that's the point at which a fuel filter's most likely to block, I visited my friendly local car breaker and came away with a pair of filters which I installed in parallel with taps before and after each filter. Y or T taps would have been a more elegant solution, but were 3 times the price of the simple fuel taps.

This means I run on one filter, with the other primed & ready to go. If I have a problem, I change to the other and have all the time I need to change the other - not long, as they're spin-on cartridges. Priming shouldn't be a problem, as the tank's higher than the filters, but I'm thinking about putting a bulb-type (outboard) pump to help things along, just to be on the safe side. Does anyone know if there's likely to be any problem using one with diesel?
 
Stemar said:
This means I run on one filter, with the other primed & ready to go. If I have a problem, I change to the other and have all the time I need to change the other - not long, as they're spin-on cartridges.
Click to expand...
So the backup filter is exactly the same CAV as the primary one, correct?
 
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